Trigger desktop notifications

Notifications show the conversation name, avatar, and new message text.
Clicking the notification opens the conversation.

js/notifications.js

@@ -0,0 +1,36 @@
+/* vim: ts=4:sw=4
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+;(function() {
+    'use strict';
+    window.Whisper = window.Whisper || {};
+
+    Whisper.Notifications = {
+      isEnabled: function(callback) {
+        return Notification.permission === 'granted' &&
+              !localStorage.getItem('disable-notifications');
+      },
+      enable: function(callback) {
+        localStorage.removeItem('disable-notifications');
+        Notification.requestPermission(function(status) {
+            callback(status);
+        });
+      },
+      disable: function() {
+        localStorage.setItem('disable-notifications', true);
+      }
+    };
+
+})();